Variable structure surge control for constant speed centrifugal compressors

This paper presents the application of active control of surge in constant speed centrifugal compressors based on the Moore–Greitzer (MG) model. Different controllers are developed for a compression system equipped with a close-coupled valve (CCV) and a throttle control valve (TCV). The combination of the two valves helps suppress surge and assists in overcoming the drawbacks of each valve when it is used individually. The presented controllers are evaluated based on many performance indices. Accordingly, a case-based variable structure controller is developed that succeeds to stabilize the system for various operating conditions and to extend the stable range well beyond the surge line. A flow extension of 76% and a stable throttle level of 0.1, with substantially decreased pressure settling times, are reported. The developed controller performs significantly better compared to other nonlinear controllers, such as the backstepping controller.